Mod[12, 0.1] gives 0.1 despite 120*0.1 == 12. I expect this is because 0.1 is not representable in binary.
QuotientRemainder[12, 0.1] gives {120, 0.} however, which is inconsistent with the result above.
Quotient[12,0.1] gives 120 which is also inconsistent with Mod.
Is this a bug or is it by design? It seems it is not safe to assume that
QuotientRemainder[a,b] == {Quotient[a,b], Mod[a,b]}
or that
Quotient[a,b]*b + Mod[a,b] == a